Multibounce Target Mitigation

ABSTRACT

A method is provided that includes a method is provided that includes transmitting a radar signal by a radar system. The method also includes receiving reflections of the radar signal from an environment by the radar system. Additionally, the method includes receiving a location of a plurality of objects in the environment by a radar processing system. The method further includes tracking a plurality of reflecting objects in the environment based on the received reflections by the radar processing system. Yet further, the method includes determining, by the radar processing system, that a received radar reflection corresponds to one of the plurality objects in the environment having an incorrect location. Moreover, the method includes revising a tracking for the one of the plurality objects in the environment having an incorrect location.

BACKGROUND

Radio detection and ranging (RADAR) systems can be used to activelyestimate range, angle, and/or Doppler frequency shift to environmentalfeatures by emitting radio signals and detecting returning reflectedsignals. Distances to radio-reflective features can be determinedaccording to the time delay between transmission and reception. Theradar system can emit a signal that varies in frequency over time, suchas a signal with a time-varying frequency ramp, and then relate thedifference in frequency between the emitted signal and the reflectedsignal to a range estimate. Some systems may also estimate relativemotion of reflective objects based on Doppler frequency shifts in thereceived reflected signals.

In some examples, directional antennas can be used for the transmissionand/or reception of signals to associate each range estimate with abearing. More generally, directional antennas can also be used to focusradiated energy on a given field of view of interest. Combining themeasured distances and the directional information allows for thesurrounding environment features to be mapped. In other examples,non-directional antennas can be alternatively used. In these examples, areceiving antenna may have a 90 degree field of view, and may beconfigured to utilize multiple channels with a phase offset to determineangle of arrival of the received signal. Thus, the radar sensor can beused, for instance, by an autonomous vehicle control system to avoidobstacles indicated by the sensor information. Some example automotiveradar systems may be configured to operate at an electromagnetic wavefrequency range of 76-77 Giga-Hertz (GHz). These radar systems may usetransmission antennas that can to focus the radiated energy into tightbeams in order to enable receiving antennas (e.g., having wide anglebeams) in the radar system to measure an environment of the vehicle withhigh accuracy.

SUMMARY

In one example, a radar system is provided. The radar system includes aradar unit configured to transmit a radar signal and receive radarreflections. The radar system also includes a memory configured to storedata related to an environment. The radar system also includes a radarprocessing system. The radar processing system is configured to receivea location of a plurality of objects in the environment. The radarprocessing system is also configured to track a plurality of reflectingobjects in the environment based on the received reflections. The radarsystem is further configured to determine that a received radarreflection corresponds to one of the plurality objects in theenvironment having an incorrect location. Additionally, the radar systemis configured to revise a tracking for the one of the plurality objectsin the environment having an incorrect location.

In another example, a method is provided that includes transmitting aradar signal by a radar system. The method also includes receivingreflections of the radar signal from an environment by the radar system.Additionally, the method includes receiving a location of a plurality ofobjects in the environment by a radar processing system. The methodfurther includes tracking a plurality of reflecting objects in theenvironment based on the received reflections by the radar processingsystem. Yet further, the method includes determining, by the radarprocessing system, that a received radar reflection corresponds to oneof the plurality objects in the environment having an incorrectlocation. Moreover, the method includes revising a tracking for the oneof the plurality objects in the environment having an incorrectlocation.

In yet another example, a non-transitory computer readable medium havingstored thereon executable instructions that, upon execution by acomputing device, cause the computing device to perform functions isprovided. The functions include causing the transmission of a radarsignal by a radar system. The functions also include receivingreflections of the radar signal from an environment by the radar system.Additionally, the functions include receiving a location of a pluralityof objects in the environment by a radar processing system. Thefunctions further include tracking a plurality of reflecting objects inthe environment based on the received reflections by the radarprocessing system. Moreover, the functions include determine that areceived radar reflection corresponds to one of the plurality objects inthe environment having an incorrect location by the radar processingsystem. The functions also include revising a tracking for the one ofthe plurality objects in the environment having an incorrect location.

In still another example, a system is provided that includes a means fortransmitting a radar signal by a radar system. The system also includesa means for receiving reflections of the radar signal from anenvironment by the radar system. Additionally, the system includes ameans for receiving a location of a plurality of objects in theenvironment by a radar processing system. The system further includes ameans for tracking a plurality of reflecting objects in the environmentbased on the received reflections by the radar processing system. Yetfurther, the system includes a means for determining that a receivedradar reflection corresponds to one of the plurality objects in theenvironment having an incorrect location. Moreover, the system includesa means for revising a tracking for the one of the plurality objects inthe environment having an incorrect location.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a functional block diagram depicting aspects of an exampleautonomous vehicle.

FIG. 2A depicts exterior views of an example autonomous vehicle.

FIG. 2B depicts sensor fields of view of an example autonomous vehicle.

FIG. 3 illustrates a plurality of vehicles within an environment of avehicle that includes a sensor, according to an example embodiment.

FIG. 4 illustrates example multibounce of a radar system.

FIG. 5 illustrates example multibounce target information of a radarsystem.

FIG. 6 illustrates an example method for use with multibounce of a radarsystem.

FIG. 7 illustrates an example method for use with multibounce to obtaintarget information of a radar system.

FIG. 8 depicts an example computer readable medium configured accordingto an example embodiment.

DETAILED DESCRIPTION

The following detailed description describes various features andfunctions of the disclosed systems and methods with reference to theaccompanying figures. In the figures, similar symbols identify similarcomponents, context dictates otherwise. The illustrative system, deviceand method embodiments described herein are not meant to be limiting. Itmay be readily understood by those skilled in the art that certainaspects of the disclosed systems, devices and methods can be arrangedand combined in a wide variety of different configurations, all of whichare contemplated herein.

Continued efforts to improve vehicle safety include the development ofautonomous vehicles equipped with accident-avoidance systems that mayhave the ability to avoid accidents. Various sensors, such as radiodetection and ranging (RADAR) sensors and light detection and ranging(LIDAR) sensors among other possibilities, may be included as part of anautonomous vehicle to detect obstacles and/or other vehicles in anenvironment of the autonomous vehicle and thereby facilitate accidentavoidance. However, recent advancements may enable sensor range andpower to increase beyond the power and range of traditional automotivesensors. Thus, due to the increased power (and associated increaserange), the sensors may be more susceptible to multipath (i.e.,inadvertent reflected signals) in some situations. The presentdisclosure is directed toward multipath of sensors.

In practice, during the operation of a radar system, a reflector (e.g.,such as an overhead roadway sign, large building, etc.) within theenvironment may cause multibounce signal to form part of the radarreflection signals. Multibounce is when a radar pulse reflects offmultiple objects (e.g., a first and a second object) before returning tothe radar unit. For example, during operation of a radar system on ahighway or a similar environment, a radar signal transmitted from avehicle may bounce off an overhead sign and then subsequently off ofanother vehicle before bouncing back off of the sign again prior toreaching the original vehicle that initially transmitted the radarsignal. In such a scenario, a conventional radar system may fail toidentify that the radar signal bounced multiple times prior to reachingthe radar system as well as where each reflection likely occurred.Rather, the conventional system might misidentify the reflected signalsas originating from an object that appears to be located on the otherside of the object that actually caused one or more of the reflections.This misidentification may cause the radar signal processing system toproduce inaccurate measurements of the environment. For instance, anyvehicles traveling nearby and in the same direction as the transmittingvehicle may appear as if they are traveling towards the transmittingvehicle rather than in the same direction as a result of a conventionalradar system misidentifying multibounce radar signals.

To overcome potential problems in multibounce scenarios, a radarprocessing system associated with a radar system may use informationknown to the transmitting vehicle, such as the positions of nearbyvehicles and/or map data, when processing received reflections of radarsignals. The radar processing system may receive this information fromvarious sources, such as prior radar measurements, sensor data fromother sensors, via wireless communication with other vehicles, and/orother sources (e.g., map databases). Particularly, the information maybe used to determine that already identified or known objects in theenvironment (e.g., nearby vehicles and overhead signs) caused thereceived reflections of signals. By determining that the reflections arecaused by known objects, the system may be able to correctly associateand assign the reflection signals to the correct objects. Thus, by usingthis technique, the radar processing system is able to reorient and/orremove the reflection signals and remove the locations of false positivedetections. Further, the radar processing system may also be able tocharacterize the main reflecting object based on the determinations madeabout the known objects detected in reflections.

Thus, in some instances, the radar processing system may determine andmonitor respective radar locations of multiple objects in thesurrounding environment. The radar processing system may also obtaininformation specifying actual locations for one or more of these objectsfrom one or more sources (e.g., sensors, databases, wirelesscommunication). The radar processing system may also perform acomparison between radar locations and actual locations of the objects.When the comparison yields a difference between the location of anobject as specified by radar and as specified by one or more othersources, the radar processing system may adjust the radar location foran object. In some instances, the radar processing system may performthis comparison process iteratively to continuously calibrate thelocation of objects as specified by radar with the locations provided byother sources.

Additionally, some radar systems may operate with high resolution inboth Doppler and range, while having low resolution in azimuth. In otherexamples, a different combination of high and low resolution may bepossible for doppler, range, and azimuth. In practice, the radarprocessing system of the present disclosure may detect and usemultibounce to refine measurements of reflecting objects. For instance,a vehicle may be able to directly image another vehicle located nearby.This direct measurement of the nearby vehicle may have high resolutionin both Doppler and range and low resolution in azimuth. Thus, the radarsystem of the vehicle may be able to accurately measure the range andDoppler of the other vehicle.

By using radar signals that perform a multibounce prior to reaching theradar system, the same vehicle may be imaged by the radar system fromanother angle (i.e., from the direction by which the reflected radarsignal hits the other vehicle). The multibounce radar signal may havehigh resolution in both Doppler and range and low resolution in azimuth.Conveniently, because the other vehicle is being imaged from anotherdirection, the low-resolution azimuth measurement of the direct radarmeasurement may be supplemented with higher resolution range informationfrom the reflected radar signal. Therefore, the radar imaging of theother vehicle may be improved through radar imaging from two differentdirections.

The embodiments disclosed herein may be used on any type of vehicle,including conventional automobiles and automobiles having an autonomousmode of operation. However, the term “vehicle” is to be broadlyconstrued to cover any moving object, including, for instance, a truck,a van, a semitrailer truck, a motorcycle, a golf cart, an off-roadvehicle, a warehouse transport vehicle, or a farm vehicle, as well as acarrier that rides on a track such as a rollercoaster, trolley, tram, ortrain car, among other examples. Furthermore, although example vehiclesare shown and described as vehicles that may be configured to operate inautonomous mode, the embodiments described herein are also applicable tovehicles that are not configured to operate autonomously. Thus, theexample vehicles are not meant to limit the present disclosure toautonomous vehicles.

FIG. 1 is a functional block diagram illustrating a vehicle 100according to an example embodiment. The vehicle 100 is configured tooperate fully or partially in an autonomous mode, and thus may bereferred to as an “autonomous vehicle.” For example, a computer system112 can control the vehicle 100 while in an autonomous mode via controlinstructions to a control system 106 for the vehicle 100. The computersystem 112 can receive information from one or more sensor systems 104and can base one or more control processes (such as setting a heading soas to avoid a detected obstacle) upon the received information in anautomated fashion.

The autonomous vehicle 100 can be fully autonomous or partiallyautonomous. In a partially autonomous vehicle some functions canoptionally be manually controlled (e.g., by a driver) some or all of thetime. Further, a partially autonomous vehicle can be configured toswitch between a fully-manual operation mode (i.e., controlled by adriver) and a partially-autonomous and/or a fully-autonomous operationmode.

The vehicle 100 includes a propulsion system 102, a sensor system 104, acontrol system 106, one or more peripherals 108, a power supply 110, acomputer system 112, and a user interface 116. The vehicle 100 mayinclude more or fewer subsystems and each subsystem can optionallyinclude multiple components. Further, each of the subsystems andcomponents of vehicle 100 can be interconnected and/or in communication.Thus, one or more of the functions of the vehicle 100 described hereincan optionally be divided between additional functional or physicalcomponents, or combined into fewer functional or physical components. Insome further examples, additional functional and/or physical componentsmay be added to the examples illustrated by FIG. 1.

The propulsion system 102 can include components operable to providepowered motion to the vehicle 100. In some embodiments the propulsionsystem 102 includes an engine/motor 118, an energy source 119, atransmission 120, and wheels/tires 121. The engine/motor 118 convertsenergy source 119 to mechanical energy. In some embodiments, thepropulsion system 102 can optionally include one or both of enginesand/or motors. For example, a gas-electric hybrid vehicle can includeboth a gasoline/diesel engine and an electric motor.

The energy source 119 represents a source of energy, such as electricaland/or chemical energy, that may, in full or in part, power theengine/motor 118. That is, the engine/motor 118 can be configured toconvert the energy source 119 to mechanical energy to operate thetransmission. In some embodiments, the energy source 119 can includegasoline, diesel, other petroleum-based fuels, propane, other compressedgas-based fuels, ethanol, solar panels, batteries, capacitors,flywheels, regenerative braking systems, and/or other sources ofelectrical power, etc. The energy source 119 can also provide energy forother systems of the vehicle 100.

The transmission 120 includes appropriate gears and/or mechanicalelements suitable to convey the mechanical power from the engine/motor118 to the wheels/tires 121. In some embodiments, the transmission 120includes a gearbox, a clutch, a differential, a drive shaft, and/oraxle(s), etc.

The wheels/tires 121 are arranged to stably support the vehicle 100while providing frictional traction with a surface, such as a road, uponwhich the vehicle 100 moves. Accordingly, the wheels/tires 121 areconfigured and arranged according to the nature of the vehicle 100. Forexample, the wheels/tires can be arranged as a unicycle, bicycle,motorcycle, tricycle, or car/truck four-wheel format. Other wheel/tiregeometries are possible, such as those including six or more wheels. Anycombination of the wheels/tires 121 of vehicle 100 may be operable torotate differentially with respect to other wheels/tires 121. Thewheels/tires 121 can optionally include at least one wheel that isrigidly attached to the transmission 120 and at least one tire coupledto a rim of a corresponding wheel that makes contact with a drivingsurface. The wheels/tires 121 may include any combination of metal andrubber, and/or other materials or combination of materials.

The sensor system 104 generally includes one or more sensors configuredto detect information about the environment surrounding the vehicle 100.For example, the sensor system 104 can include a Global PositioningSystem (GPS) 122, an inertial measurement unit (IMU) 124, a RADAR unit126, a laser rangefinder/LIDAR unit 128, a camera 130, and/or amicrophone 131. The sensor system 104 could also include sensorsconfigured to monitor internal systems of the vehicle 100 (e.g., 02monitor, fuel gauge, engine oil temperature, wheel speed sensors, etc.).One or more of the sensors included in sensor system 104 could beconfigured to be actuated separately and/or collectively in order tomodify a position and/or an orientation of the one or more sensors.

The GPS 122 is a sensor configured to estimate a geographic location ofthe vehicle 100. To this end, GPS 122 can include a transceiver operableto provide information regarding the position of the vehicle 100 withrespect to the Earth.

The IMU 124 can include any combination of sensors (e.g., accelerometersand gyroscopes) configured to sense position and orientation changes ofthe vehicle 100 based on inertial acceleration.

The RADAR unit 126 can represent a system that utilizes radio signals tosense objects within the local environment of the vehicle 100. In someembodiments, in addition to sensing the objects, the RADAR unit 126and/or the computer system 112 can additionally be configured to sensethe speed and/or heading of the objects.

Similarly, the laser rangefinder or LIDAR unit 128 can be any sensorconfigured to sense objects in the environment in which the vehicle 100is located using lasers. The laser rangefinder/LIDAR unit 128 caninclude one or more laser sources, a laser scanner, and one or moredetectors, among other system components. The laser rangefinder/LIDARunit 128 can be configured to operate in a coherent (e.g., usingheterodyne detection) or an incoherent detection mode.

The camera 130 can include one or more devices configured to capture aplurality of images of the environment surrounding the vehicle 100. Thecamera 130 can be a still camera or a video camera. In some embodiments,the camera 130 can be mechanically movable such as by rotating and/ortilting a platform to which the camera is mounted. As such, a controlprocess of vehicle 100 may be implemented to control the movement ofcamera 130.

The sensor system 104 can also include a microphone 131. The microphone131 can be configured to capture sound from the environment surroundingvehicle 100. In some cases, multiple microphones can be arranged as amicrophone array, or possibly as multiple microphone arrays.

The control system 106 is configured to control operation(s) regulatingacceleration of the vehicle 100 and its components. To effectacceleration, the control system 106 includes a steering unit 132,throttle 134, brake unit 136, a sensor fusion algorithm 138, a computervision system 140, a navigation/pathing system 142, and/or an obstacleavoidance system 144, etc.

The steering unit 132 is operable to adjust the heading of vehicle 100.For example, the steering unit can adjust the axis (or axes) of one ormore of the wheels/tires 121 so as to effect turning of the vehicle. Thethrottle 134 is configured to control, for instance, the operating speedof the engine/motor 118 and, in turn, adjust forward acceleration of thevehicle 100 via the transmission 120 and wheels/tires 121. The brakeunit 136 decelerates the vehicle 100. The brake unit 136 can usefriction to slow the wheels/tires 121. In some embodiments, the brakeunit 136 inductively decelerates the wheels/tires 121 by a regenerativebraking process to convert kinetic energy of the wheels/tires 121 toelectric current.

The sensor fusion algorithm 138 is an algorithm (or a computer programproduct storing an algorithm) configured to accept data from the sensorsystem 104 as an input. The data may include, for example, datarepresenting information sensed at the sensors of the sensor system 104.The sensor fusion algorithm 138 can include, for example, a Kalmanfilter, Bayesian network, etc. The sensor fusion algorithm 138 providesassessments regarding the environment surrounding the vehicle based onthe data from sensor system 104. In some embodiments, the assessmentscan include evaluations of individual objects and/or features in theenvironment surrounding vehicle 100, evaluations of particularsituations, and/or evaluations of possible interference between thevehicle 100 and features in the environment (e.g., such as predictingcollisions and/or impacts) based on the particular situations.

The computer vision system 140 can process and analyze images capturedby camera 130 to identify objects and/or features in the environmentsurrounding vehicle 100. The detected features/objects can includetraffic signals, roadway boundaries, other vehicles, pedestrians, and/orobstacles, etc. The computer vision system 140 can optionally employ anobject recognition algorithm, a Structure From Motion (SFM) algorithm,video tracking, and/or available computer vision techniques to effectcategorization and/or identification of detected features/objects. Insome embodiments, the computer vision system 140 can be additionallyconfigured to map the environment, track perceived objects, estimate thespeed of objects, etc.

The navigation and pathing system 142 is configured to determine adriving path for the vehicle 100. For example, the navigation andpathing system 142 can determine a series of speeds and directionalheadings to effect movement of the vehicle along a path thatsubstantially avoids perceived obstacles while generally advancing thevehicle along a roadway-based path leading to an ultimate destination,which can be set according to user inputs via the user interface 116,for example. The navigation and pathing system 142 can additionally beconfigured to update the driving path dynamically while the vehicle 100is in operation on the basis of perceived obstacles, traffic patterns,weather/road conditions, etc. In some embodiments, the navigation andpathing system 142 can be configured to incorporate data from the sensorfusion algorithm 138, the GPS 122, and one or more predetermined maps soas to determine the driving path for vehicle 100.

The obstacle avoidance system 144 can represent a control systemconfigured to identify, evaluate, and avoid or otherwise negotiatepotential obstacles in the environment surrounding the vehicle 100. Forexample, the obstacle avoidance system 144 can effect changes in thenavigation of the vehicle by operating one or more subsystems in thecontrol system 106 to undertake swerving maneuvers, turning maneuvers,braking maneuvers, etc. In some embodiments, the obstacle avoidancesystem 144 is configured to automatically determine feasible(“available”) obstacle avoidance maneuvers on the basis of surroundingtraffic patterns, road conditions, etc. For example, the obstacleavoidance system 144 can be configured such that a swerving maneuver isnot undertaken when other sensor systems detect vehicles, constructionbarriers, other obstacles, etc. in the region adjacent the vehicle thatwould be swerved into. In some embodiments, the obstacle avoidancesystem 144 can automatically select the maneuver that is both availableand maximizes safety of occupants of the vehicle. For example, theobstacle avoidance system 144 can select an avoidance maneuver predictedto cause the least amount of acceleration in a passenger cabin of thevehicle 100.

The vehicle 100 also includes peripherals 108 configured to allowinteraction between the vehicle 100 and external sensors, othervehicles, other computer systems, and/or a user, such as an occupant ofthe vehicle 100. For example, the peripherals 108 for receivinginformation from occupants, external systems, etc. can include awireless communication system 146, a touchscreen 148, a microphone 150,and/or a speaker 152.

In some embodiments, the peripherals 108 function to receive inputs fora user of the vehicle 100 to interact with the user interface 116. Tothis end, the touchscreen 148 can both provide information to a user ofvehicle 100, and convey information from the user indicated via thetouchscreen 148 to the user interface 116. The touchscreen 148 can beconfigured to sense both touch positions and touch gestures from auser's finger (or stylus, etc.) via capacitive sensing, resistancesensing, optical sensing, a surface acoustic wave process, etc. Thetouchscreen 148 can be capable of sensing finger movement in a directionparallel or planar to the touchscreen surface, in a direction normal tothe touchscreen surface, or both, and may also be capable of sensing alevel of pressure applied to the touchscreen surface. An occupant of thevehicle 100 can also utilize a voice command interface. For example, themicrophone 150 can be configured to receive audio (e.g., a voice commandor other audio input) from a user of the vehicle 100. Similarly, thespeakers 152 can be configured to output audio to the user of thevehicle 100.

In some embodiments, the peripherals 108 function to allow communicationbetween the vehicle 100 and external systems, such as devices, sensors,other vehicles, etc. within its surrounding environment and/orcontrollers, servers, etc., physically located far from the vehicle thatprovide useful information regarding the vehicle's surroundings, such astraffic information, weather information, etc. For example, the wirelesscommunication system 146 can wirelessly communicate with one or moredevices directly or via a communication network. The wirelesscommunication system 146 can optionally use 3G cellular communication,such as Code-Division Multiple Access (CDMA), Evolution-Data Optimized(EV-DO), Global System for Mobile communications (GSM)/General PacketRadio Surface (GPRS), and/or 4G cellular communication, such asWorldwide Interoperability for Microwave Access (WiMAX) or Long-TermEvolution (LTE). Additionally or alternatively, wireless communicationsystem 146 can communicate with a wireless local area network (WLAN),for example, using WiFi. In some embodiments, wireless communicationsystem 146 could communicate directly with a device, for example, usingan infrared link, Bluetooth®, and/or ZigBee®. The wireless communicationsystem 146 can include one or more dedicated short-range communication(DSRC) devices that can include public and/or private datacommunications between vehicles and/or roadside stations. Other wirelessprotocols for sending and receiving information embedded in signals,such as various vehicular communication systems, can also be employed bythe wireless communication system 146 within the context of the presentdisclosure.

As noted above, the power supply 110 can provide power to components ofvehicle 100, such as electronics in the peripherals 108, computer system112, sensor system 104, etc. The power supply 110 can include arechargeable lithium-ion or lead-acid battery for storing anddischarging electrical energy to the various powered components, forexample. In some embodiments, one or more banks of batteries can beconfigured to provide electrical power. In some embodiments, the powersupply 110 and energy source 119 can be implemented together, as in someall-electric cars.

Many or all of the functions of vehicle 100 can be controlled viacomputer system 112 that receives inputs from the sensor system 104,peripherals 108, etc., and communicates appropriate control signals tothe propulsion system 102, control system 106, peripherals 108, etc. toeffect automatic operation of the vehicle 100 based on its surroundings.Computer system 112 includes at least one processor 113 (which caninclude at least one microprocessor) that executes instructions 115stored in a non-transitory computer readable medium, such as the datastorage 114. The computer system 112 may also represent a plurality ofcomputing devices that serve to control individual components orsubsystems of the vehicle 100 in a distributed fashion.

In some embodiments, data storage 114 contains instructions 115 (e.g.,program logic) executable by the processor 113 to execute variousfunctions of vehicle 100, including those described above in connectionwith FIG. 1. Data storage 114 may contain additional instructions aswell, including instructions to transmit data to, receive data from,interact with, and/or control one or more of the propulsion system 102,the sensor system 104, the control system 106, and the peripherals 108.

In addition to the instructions 115, the data storage 114 may store datasuch as roadway maps, path information, among other information. Suchinformation may be used by vehicle 100 and computer system 112 duringoperation of the vehicle 100 in the autonomous, semi-autonomous, and/ormanual modes to select available roadways to an ultimate destination,interpret information from the sensor system 104, etc.

The vehicle 100, and associated computer system 112, providesinformation to and/or receives input from, a user of vehicle 100, suchas an occupant in a passenger cabin of the vehicle 100. The userinterface 116 can accordingly include one or more input/output deviceswithin the set of peripherals 108, such as the wireless communicationsystem 146, the touchscreen 148, the microphone 150, and/or the speaker152 to allow communication between the computer system 112 and a vehicleoccupant.

The computer system 112 controls the operation of the vehicle 100 basedon inputs received from various subsystems indicating vehicle and/orenvironmental conditions (e.g., propulsion system 102, sensor system104, and/or control system 106), as well as inputs from the userinterface 116, indicating user preferences. For example, the computersystem 112 can utilize input from the control system 106 to control thesteering unit 132 to avoid an obstacle detected by the sensor system 104and the obstacle avoidance system 144. The computer system 112 can beconfigured to control many aspects of the vehicle 100 and itssubsystems. Generally, however, provisions are made for manuallyoverriding automated controller-driven operation, such as in the eventof an emergency, or merely in response to a user-activated override,etc.

The components of vehicle 100 described herein can be configured to workin an interconnected fashion with other components within or outsidetheir respective systems. For example, the camera 130 can capture aplurality of images that represent information about an environment ofthe vehicle 100 while operating in an autonomous mode. The environmentmay include other vehicles, traffic lights, traffic signs, road markers,pedestrians, etc. The computer vision system 140 can categorize and/orrecognize various aspects in the environment in concert with the sensorfusion algorithm 138, the computer system 112, etc. based on objectrecognition models pre-stored in data storage 114, and/or by othertechniques.

Although the vehicle 100 is described and shown in FIG. 1 as havingvarious components of vehicle 100, e.g., wireless communication system146, computer system 112, data storage 114, and user interface 116,integrated into the vehicle 100, one or more of these components canoptionally be mounted or associated separately from the vehicle 100. Forexample, data storage 114 can exist, in part or in full, separate fromthe vehicle 100, such as in a cloud-based server, for example. Thus, oneor more of the functional elements of the vehicle 100 can be implementedin the form of device elements located separately or together. Thefunctional device elements that make up vehicle 100 can generally becommunicatively coupled together in a wired and/or wireless fashion.

FIG. 2A shows an example vehicle 200 that can include some or all of thefunctions described in connection with vehicle 100 in reference toFIG. 1. In particular, FIG. 2A shows various different views of vehicle200. Although vehicle 200 is illustrated in FIG. 2A as a four-wheelvan-type car for illustrative purposes, the present disclosure is not solimited. For instance, the vehicle 200 can represent a truck, a van, asemi-trailer truck, a motorcycle, a golf cart, an off-road vehicle, or afarm vehicle, etc.

The example vehicle 200 includes a sensor unit 202, a wirelesscommunication system 204, RADAR units 206, laser rangefinder units 208,and a camera 210. Furthermore, the example vehicle 200 can include anyof the components described in connection with vehicle 100 of FIG. 1.The RADAR unit 206 and/or laser rangefinder unit 208 can actively scanthe surrounding environment for the presence of potential obstacles andcan be similar to the RADAR unit 126 and/or laser rangefinder/LIDAR unit128 in the vehicle 100.

The sensor unit 202 is mounted atop the vehicle 200 and includes one ormore sensors configured to detect information about an environmentsurrounding the vehicle 200, and output indications of the information.For example, sensor unit 202 can include any combination of cameras,RADARs, LIDARs, range finders, and acoustic sensors. The sensor unit 202can include one or more movable mounts that could be operable to adjustthe orientation of one or more sensors in the sensor unit 202. In oneembodiment, the movable mount could include a rotating platform thatcould scan sensors so as to obtain information from each directionaround the vehicle 200. In another embodiment, the movable mount of thesensor unit 202 could be moveable in a scanning fashion within aparticular range of angles and/or azimuths. The sensor unit 202 could bemounted atop the roof of a car, for instance, however other mountinglocations are possible. Additionally, the sensors of sensor unit 202could be distributed in different locations and need not be collocatedin a single location. Some possible sensor types and mounting locationsinclude RADAR unit 206 and laser rangefinder unit 208. Furthermore, eachsensor of sensor unit 202 can be configured to be moved or scannedindependently of other sensors of sensor unit 202.

In an example configuration, one or more RADAR scanners (e.g., the RADARunit 206) can be located near the front of the vehicle 200, to activelyscan the region in front of the car 200 for the presence ofradio-reflective objects. A RADAR scanner can be situated, for example,in a location suitable to illuminate a region including a forward-movingpath of the vehicle 200 without occlusion by other features of thevehicle 200. For example, a RADAR scanner can be situated to be embeddedand/or mounted in or near the front bumper, front headlights, cowl,and/or hood, etc. Furthermore, one or more additional RADAR scanningdevices can be located to actively scan the side and/or rear of thevehicle 200 for the presence of radio-reflective objects, such as byincluding such devices in or near the rear bumper, side panels, rockerpanels, and/or undercarriage, etc.

The wireless communication system 204 could be located on the roof ofthe vehicle 200 as depicted in FIG. 2A. Alternatively, the wirelesscommunication system 204 could be located, fully or in part, elsewhere.The wireless communication system 204 may include wireless transmittersand receivers that could be configured to communicate with devicesexternal or internal to the vehicle 200. Specifically, the wirelesscommunication system 204 could include transceivers configured tocommunicate with other vehicles and/or computing devices, for instance,in a vehicular communication system or a roadway station. Examples ofsuch vehicular communication systems include dedicated short rangecommunications (DSRC), radio frequency identification (RFID), and otherproposed communication standards directed towards intelligent transportsystems.

The camera 210 can be a photo-sensitive instrument, such as a stillcamera, a video camera, etc. that is configured to capture a pluralityof images of the environment of the vehicle 200. To this end, the camera210 can be configured to detect visible light, and can additionally oralternatively be configured to detect light from other portions of thespectrum, such as infrared or ultraviolet light. The camera 210 can be atwo-dimensional detector, and can optionally have a three-dimensionalspatial range of sensitivity. In some embodiments, the camera 210 caninclude, for example, a range detector configured to generate atwo-dimensional image indicating distance from the camera 210 to anumber of points in the environment. To this end, the camera 210 may useone or more range detecting techniques.

For example, the camera 210 can provide range information by using astructured light technique in which the vehicle 200 illuminates anobject in the environment with a predetermined light pattern, such as agrid or checkerboard pattern and uses the camera 210 to detect areflection of the predetermined light pattern from environmentalsurroundings. Based on distortions in the reflected light pattern, thevehicle 200 can determine the distance to the points on the object. Thepredetermined light pattern may comprise infrared light or radiation atother suitable wavelengths for such measurements.

The camera 210 can be mounted inside a front windshield of the vehicle200. Specifically, the camera 210 can be situated to capture images froma forward-looking view with respect to the orientation of the vehicle200. Other mounting locations and viewing angles of camera 210 can alsobe used, either inside or outside the vehicle 200. Further, the camera210 can have associated optics operable to provide an adjustable fieldof view. Further, the camera 210 can be mounted to vehicle 200 with amovable mount to vary a pointing angle of the camera 210, such as via apan/tilt mechanism.

FIG. 2B illustrates an example autonomous vehicle 250 having varioussensor fields of view. As previously discussed with respect to FIG. 2A,the vehicle 250 may contain a plurality of sensors. The locations of thevarious sensors may correspond to the locations of the sensors disclosedin FIG. 2A. However, in some instances, the sensors may have otherlocations. Sensors locations are omitted from FIG. 2B for simplicity ofthe drawing. For each sensor unit of vehicle 250, FIG. 2B shows arespective field of view. The field of view of a sensor may include anangular region over which the sensor may detect objects and a range thatcorresponds to maximum distance from the sensor at which the sensor mayreliable detect objects.

The vehicle 250 may include six radar units. A first radar unit may belocated on the front-left of the vehicle and have an angular field ofview corresponding to the angular portion of field of view 252A. Asecond radar unit may be located on the front-right of the vehicle andhave an angular field of view corresponding to the angular portion offield of view 252B. A third radar unit may be located on the rear-leftof the vehicle and have an angular field of view corresponding to theangular portion of field of view 252C. A fourth radar unit may belocated on the rear-right of the vehicle and have an angular field ofview corresponding to the angular portion of field of view 252D. A fifthradar unit may be located on the left side of the vehicle and have anangular field of view corresponding to the angular portion of field ofview 252E. A sixth radar unit may be located on the right side of thevehicle and have an angular field of view corresponding to the angularportion of field of view 252F. Each of the six radar units may beconfigured with a scannable beamwidth of 90 degrees. A radar beamwidthmay be smaller than 90 degrees, but each radar unit may be able to steerthe radar beam across the 90-degree field of view.

A first LIDAR unit of the vehicle 250 may be configured to scan the full360-degree region around the vehicle as shown by an angular field ofview corresponding to the angular portion of field of view 254. A secondLIDAR unit of the vehicle 250 may be configured to scan a region smallerthan the 360-degree region around the vehicle. In one example, thesecond LIDAR unit may have a field of view smaller than 10 degrees inthe horizontal plant as shown by an angular field of view correspondingto the angular portion of field of view 254.

Additionally, the vehicle may also include at least one camera. Thecamera may be an optical camera and/or an infrared camera.

In addition to the field of view for each of the various sensors ofvehicle 250, each sensor may also have a corresponding range. In oneexample, the range of the radar units may be greater than the range ofeither LIDAR unit, as shown by the field of the views of the radar units252A-252E extending further than the fields of view for the LIDAR units254 and 256. Additionally, the second LIDAR unit may have a range thatis greater than a range of the first LIDAR unit, as shown by field ofview 256 extending further than field of view 254. In various examples,the range of the camera may be greater than or less than the range ofthe other sensors.

FIG. 3 illustrates a plurality of vehicles 312 a-312 c within anenvironment of a vehicle 302 that includes a sensor 306, according to anexample embodiment. Although sensor 306 is shown on the roof of vehicle302, it should be understood that sensor 306 may be located in thelocation(s) described with respect to FIG. 2B and have a field of viewsimilar to that described with respect to FIG. 2B.

The vehicles 302 and 312 a-c may be similar to the vehicles 100, 200,302 a-302 d of FIGS. 1-3. For example, the vehicle 302 may include thesensor 306 (e.g., RADAR, LIDAR, etc.) similar to the radar unit 206and/or the lidar unit 202 or 208 of the vehicle 200. Further, thevehicle 302 includes a mount 304 (“steering device”) configured toadjust a direction of the sensor 306. The mount 304, for example, may bea moveable mount comprising materials suitable for supporting the sensor306 and may be operated by a control system (not shown) to rotate thesensor 306 about a mount axis to modify the direction of the sensor 306.Alternatively, the mount 304 may modify the direction of the sensor 306in a different manner. For example, the mount 304 (e.g., steeringdevice) may translate the sensor 306 along a horizontal plane, etc.

As illustrated in FIG. 3, the vehicles 302 and 312 a-312 c are travelingon a road 310. The road 310 may have various objects located near theroadway that are not vehicles, such as buildings, embankments, walls,signs, etc. As the vehicle 302 operates on the roadway, it may usesensors to detect and determine locations for objects in the environmentaround the vehicle 302.

However, in some examples, the objects near the roadway may reflectsignals transmitted by the sensors. These reflected signals may bereceived by the vehicle 302. The reflected signals may make one or moreobjects appear as if they exist in a position different from theiractual position. Additionally, the reflections may also make the objectsappear as if they are moving in different directions than they reallyare. Thus, it may be desirable to determine when reflections are presentin a sensor system.

FIG. 4 illustrates example multibounce of a radar system. As shown inFIG. 4, a first vehicle 402 may be operating on a roadway nearby twoother vehicles 404A and 404B. The first vehicle 402 may be similar tothe vehicles described with respect to FIGS. 1-3.

Similar to many highways and other types of roads, the roadway mayinclude signs , such as the overhead sign 406. The first vehicle 402 maytransmit a signal 408 by one of its sensors, such as a radar sensor.Upon leaving the first vehicle 402, the signal 408 may encounter andreflect off various objects in the environment, including overhead sign406 prior to reception back at one or more sensors of the first vehicle402. In some examples, a set of reflected signals received back by thefirst vehicle 402 may include one or more signals that engaged in amultibounce action prior to reaching the first vehicle 402 (e.g., asignal may reflect off: (i) the overhead sign 406, (ii) a vehicle (e.g.,vehicles 402, 404A-404B), and (iii) back off the overhead sign 406before reception at the first vehicle 402).

As indicated above, a signal that reflects off multiple surfaces in theenvironment prior to reaching the radar system (e.g., the overhead sign406 and one or more vehicles) for processing may be called a multibounce(or multipath) signal. In some examples, a multibounce signal may becaused by other secondary reflectors in the environment, such asroadside objects, signs, and/or by vehicles themselves (such as a largesemi-truck trailer). Processing one or more multibounce signals cancause the target objects that reflected the signals by way of themultibounce to appear to be located in an incorrect position. Forexample, the multibounce reflections may cause the vehicle 404A toappear at the location of the vehicle 452A, the vehicle 404B to appearat the location of the vehicle 452B, and/or the vehicle 402 to appear atthe location of the vehicle 452C. Thus, the reflected sensor signals maymake it seem that vehicles 402, 404A, and 404B are driving towardvehicle 402 despite that the vehicles are all actually traveling in thesame direction as shown in FIG. 4. In other examples, the virtualvehicle may be located in or appear to move in a direction other thantowards the vehicle 402. Thus, it may be desirable to identify andmitigate the virtual vehicle that may appear in sensor data frommultibounce.

FIG. 5 illustrates example multibounce target information of a radarsystem. As shown in FIG. 5, a vehicle 502 may include one or more sensorunits, such as multiple radar sensors. The vehicle 502 may be operatingin the vicinity of other vehicles (e.g., a vehicle 504) and otherelements within a roadway environment (e.g., an overhead sign 506 or,any other secondary reflecting object). During the operation of thevehicle 504, the sensor system (e.g., a radar system) may transmit afirst sensor signal 508A and a second sensor signal 508B. The firstsensor signal 508A may reflect off the other vehicle 504 back to thesensor of the vehicle 502 as a primary reflection. The second sensorsignal 508B may reflect off the overhead sign 506 as a reflected signal510 then reflect off the other vehicle 504. Once the reflected signal510 reflects from the other vehicle 508B, the reflected signal 510 mayreflect off the overhead sign 506 again prior to reception by a sensorof the vehicle 502 as a secondary reflection (i.e., a reflection thatbounced off a secondary reflecting object).

As previously discussed, some sensor systems, such as radar systems, mayoperate with high resolution in both Doppler and range, while having lowresolution in azimuth (i.e., angular resolution). As shown in FIG. 5,ambiguity region 512A may be representative of the range, Doppler, andazimuth ambiguity of the primary reflection from transmitted signal508A. Additionally, ambiguity region 512B may be representative of therange, Doppler, and azimuth ambiguity of the secondary reflection fromtransmitted signal 508B. Both ambiguity regions 512A and 512B representthe uncertainty in sensor measurements. As shown, both have a muchlarger azimuth extent due to the larger azimuth ambiguity of the sensorcompared to range and doppler ambiguity.

However, because the vehicle 502 receives sensor data from two differentangles of vehicle 504, a radar processing system of the vehicle 504 maybe able to combine the sensor data of the two measurements to decreasethe azimuth ambiguity 512A of the primary reflection 508B. Through theprimary reflection from transmitted signal 508A and the secondaryreflection from transmitted signal 508B, the same vehicle 504 may beimaged by the sensor system from another angle (i.e., from the directionby which the reflected radar signal hits the other vehicle).Conveniently, because the other vehicle 504 is being imaged from anotherdirection, the low-resolution azimuth measurement of the primary sensormeasurement may be supplemented with higher resolution range informationfrom the secondary sensor measurement. Thus, the overall azimuthambiguity of the secondary vehicle 504 may be reduced as the rangemeasurement of the secondary reflection from transmitted signal 508B maybe used to determine azimuth information that is more precise in thedirection of the primary reflection from transmitted signal 508A.

FIG. 6 illustrates an example method 600 for use with multibounce of aradar system, according to an example embodiment. Method 600 shown inFIG. 6 presents an embodiment of a method that could be used with one ormore of the vehicles described with respect to FIGS. 1-5. Method 600 mayinclude one or more operations, functions, or actions as illustrated byone or more of blocks 602-614. Although the blocks are illustrated in asequential order, these blocks may in some instances be performed inparallel, and/or in a different order than those described herein. Also,the various blocks may be combined into fewer blocks, divided intoadditional blocks, and/or removed based upon the desired implementation.

In addition, for both method 600 and method 700 shown in FIG. 7 andother processes and methods disclosed herein, the flowchart showsfunctionality and operation of one possible implementation of presentembodiments. In this regard, each block may represent a module, asegment, a portion of a manufacturing or operation process, or a portionof program code, which includes one or more instructions executable by aprocessor, such as a processor of a radar processing system, forimplementing specific logical functions or steps in the process. Theprogram code may be stored on any type of computer readable medium, forexample, such as a storage device including a disk or hard drive. Thecomputer readable medium may include non-transitory computer readablemedium, for example, such as computer-readable media that stores datafor short periods of time like register memory, processor cache andRandom Access Memory (RAM). The computer readable medium may alsoinclude non-transitory media, such as secondary or persistent long termstorage, like read only memory (ROM), optical or magnetic disks,compact-disc read only memory (CD-ROM), for example. The computerreadable media may also be any other volatile or non-volatile storagesystems. The computer readable medium may be considered a computerreadable storage medium, for example, or a tangible storage device.

In addition, for the method 600 and other processes and methodsdisclosed herein, each block in FIG. 6 may represent circuitry that iswired to perform the specific logical functions in the process, forexample.

At block 602, the method 600 includes transmitting a radar signal by aradar system. The radar system may operate by transmitting a series ofradar pulses into the surrounding environment of the vehicle. A vehiclemay include a radar system that includes one or more radar units. Insome examples, a vehicle may have one radar unit. In other examples, avehicle may include several radar units, each having a respectiveorientation. A radar unit may include a radar antenna and radarhardware, such as signal generators, signal processors, digital toanalog (D to A) converters, and analog to digital (A to D) converters.The radar units may be configured to transmit radar signals into theenvironment of the vehicle. In some examples, each radar unit may becoupled to a radar processor. The radar processor may control thesignals transmitted by a respective radar unit. The radar unit may useone or more antennas to transmit the radar signal. For example, theradar processor may be in communication with one or more radar units.The radar processor may send signals to each radar unit instructing itto transmit radar signals.

At block 604, the method 600 includes receiving reflections of the radarsignal from an environment by the radar system. Once a radar signal istransmitted at block 602, the radar unit may use an antenna to receiveradar reflection signals reflected back to the radar unit from theenvironment of the vehicle. At block 604, the radar system may receiveradar reflections for each of the transmitted radar pulses. The radarunit may use at least one antenna to receive the radar signals. In someexamples, the radar unit may use the same antennas that transmitted atblock 602. In other examples, the radar unit may use different antennasthan the transmission antennas.

When radar signals are received by the antennas, they may be convertedfrom an analog signal into a digital signal. The digital signal may becommunicated to the radar processor. In some other examples, the radarprocessor may receive analog signals instead of digital signals. Theradar processor may use the received signals to determine the parametersof the objects that reflected the radar signals. The radar processor maydetermine a range to reflecting objects, a doppler shift of thereflecting objects, and an azimuth extent of the objects. Additionally,the radar processor may determine a location and a movement of thereflecting objects.

At block 606, the method 600 includes receiving a location of aplurality of objects in the environment by a radar processing system.The radar processing system may receive an input of locations of aplurality of objects in the environment of the vehicle. In someexamples, receiving a location of a plurality of objects in theenvironment includes receiving object data from a sensor. For example,the locations may be determined based on data from optical cameras,infrared cameras, LIDAR, or other sensors. In another example, receivinga location of a plurality of objects in the environment comprisesreceiving object data from map data stored in a memory.

The map data may be pre-stored in a memory of the vehicle. In someexamples, the map data may be received by the vehicle from a remotecomputing system. The objects in the map data may be provided by theremote server as well. In other examples, the processing system of thevehicle may locate the objects with respective locations in the map databased on sensor data collected by the vehicle. For example, the map datamay include some objects, such as static location objects that may be inthe environment of the vehicle. The sensor system of the vehicle may beable to supplement the map data and add locations of other objects(e.g., pedestrians and other vehicles) to the map data. In someexamples, the sensor-supplemented map data may be objects that do nothave a fixed location in the environment of the vehicle.

In some other examples, the method 600 may omit block 606. In theseexamples, the system may function exclusively based on the radar datathat the vehicle receives.

At block 608, the method 600 includes tracking a plurality of reflectingobjects in the environment based on the received reflections by theradar processing system. Based on the received radar signals, the radarprocessing system may track a plurality of objects that produce radarreflection. By tracking objects, the radar system may determine alocation and movement (e.g., range, doppler, and azimuth extent) of thevarious objects that caused radar reflections. With each subsequentreceived radar pulse, the radar system may update the locationinformation. Thus, through a series of received radar pulses, the radarsystem may be able to revise the location information and track therelative locations of the various reflectors.

In some examples, at block 608, a processor of the vehicle, such as theradar processor or another processor, may associate the trackedreflecting objects with various known objects. Thus, the tracking mayinclude a processor associating the radar reflection signals with knownobjects in the map data.

At block 610, the method 600 includes determining, by the radarprocessing system, that a received radar reflection corresponds to oneof the plurality objects in the environment having an incorrectlocation. In one example, the system may flag tracked objects that donot correspond with objects in the map data. For example, one radarreflection may correspond to the location of another vehicle in the mapdata (e.g., another vehicle that was located based on data from othersensors). A radar reflection that corresponds with a known object maynot be flagged. However, another radar reflection may correspond to thelocation that is not known or expected to have any objects. A radarreflection that corresponds with no known objects may be flagged. Thesystem may perform an analysis on the flagged objects to determine ifthe flagged objects are actual objects in the environment or if they arevirtual objects caused by radar multibounce.

In some examples, block 610 may include determining a secondaryreflecting object that caused the incorrect location. At block 610, theprocessor may determine that a potential secondary reflecting object islocated in the environment of the vehicle. For example, this secondaryreflecting object may be an overhead road sign that is identified in themap data. In another example, the radar processing system may be able toidentify a secondary reflecting object based on received radarreflections (as the secondary reflecting object may also act as aprimary reflecting object and directly reflect radar signals back to thevehicle that transmitted the radar signals).

Based on the identification of a secondary reflecting object, the systemmay determine if the secondary reflecting object may cause virtualobjects to appear based on the position of the vehicle, the position ofthe secondary reflecting object, and the position of known objects. Forexample, as seen in FIG. 4, the secondary reflecting object causesvirtual objects for each of the three vehicles. Thus, the system mayknow the positions of the three vehicles based on map data and othersensor data. The system may have flagged the three virtual vehicles asnot being associated with known objects. The system may then use analgorithm, such as ray tracing or another algorithm, to determine if thelocation of the virtual object corresponds to an expected location ofthe virtual object based on the locations of the position of thevehicle, the position of the secondary reflecting object, and theposition of known vehicles. If the location corresponds, the system maydetermine that the virtual objects have incorrect locations identified.

Additionally, at block 610, the vehicle may communicate informationrelated to the secondary reflecting object to a remote computing system.For example, the vehicle may send data to the remote computing system sothat the remote computing system may update global map data (i.e., mapdata provided to all vehicles) so that other vehicles may be able tomore easily identify the secondary reflecting object.

At block 612, the method 600 includes revising a tracking for the one ofthe plurality of objects in the environment having an incorrectlocation. In response to the system determining that a tracked objecthas an incorrect location, the system may revise the tracking. In someexamples, the system may revise the tracking by stopping tracking anobject with an incorrect location.

It may be desirable to stop tracking an object when it is determinedthat the tracked object is not a real object, such as a false radarreturn. It may also be desirable to stop tracking an object when thetracked object is determined to be a virtual object that corresponds toanother already-tracked object. For instance, an object may already betracked with either radar or some other sensor. When the object with theincorrect location is determined to be the same object, the track may bestopped so that the true location of the object will be tracked.

In another example, revising the tracking may include revising alocation of the one of the plurality objects in the environment havingan incorrect location. In some instances, the system may determine acorrect location for the object that was initially tracked with theincorrect location. Thus, the system may revise a location of the objectand continue tracking it. For example, when an object is initiallytracked is a virtual object based on reflected signals, the system maydetermine the object's correct location (such as by way of ray tracing,as previously described) and continue to track the object at the correctlocation. Additionally, revising the tracking may also include revisinga movement direction of one of the plurality objects in the environmenthaving an incorrect location. For example, the system may determine atrue direction of travel and revise the tracking to include both thecorrect location and the correct direction of travel, such as in similarmanners used to determine the true location. For example, based on thereflections caused by the secondary reflector, the system may be able todetermine a true direction of travel for the objects having an incorrectlocation.

FIG. 7 illustrates an example method 700 for use with multibounce toobtain target information of a radar system. At block 702, the method700 includes transmitting a radar signal by a radar system. Aspreviously discussed, the radar system may operate by transmitting aseries of radar pulses into the environment of the vehicle. A vehiclemay include a radar system that includes one or more radar units. Atblock 702 each radar unit, or a subset of radar units, may transmit aseries of radar pulses. In other examples, a vehicle may include severalradar units, each having a respective orientation. A radar unit mayinclude a radar antenna and radar hardware, such as signal generators,signal processors, digital to analog (D to A) converters, and analog todigital (A to D) converters. The radar units may be configured totransmit radar signals into the environment of the vehicle. In someexamples, each radar unit may be coupled to a radar processor. The radarprocessor may control the signals transmitted by a respective radarunit. The radar unit may use one or more antennas to transmit the radarsignal. For example, the radar processor may be in communication withone or more radar units. The radar processor may send signals to eachradar unit instructing it to transmit radar signals.

At block 704, the method 700 includes receiving reflections of theplurality of radar signals from an environment by the radar system. Oncea radar signal signal is transmitted at block 702, the radar unit mayuse an antenna to receive radar reflection signals reflected back to theradar unit from the environment of the vehicle. At block 704, the radarsystem may receive radar reflections for each of the transmitted radarpulses. The radar unit may use at least one antenna to receive the radarsignals.

In some examples, the radar unit may use the same antennas thattransmitted at block 702. In other examples, the radar unit may usedifferent antennas than the transmission antennas. Additionally, in someexamples, a respective radar unit may receive radar reflectionscorresponding to reflections of the radar signals transmitted by thatradar unit. Thus, each radar unit may operate to transmit and receiveindependent of each other radar unit. In other examples, a radar unitmay receive radar signals that are transmitted by a different radarunit.

When radar signals are received by the antennas, they may be convertedfrom an analog signal into a digital signal. The digital signal may becommunicated to the radar processor. In some other examples, the radarprocessor may receive analog signals instead of digital signals. Theradar processor may use the received signals to determine the parametersof the objects that reflected the radar signals. The radar processor maydetermine a range to reflecting objects, a doppler shift of thereflecting objects, and an azimuth extent of the objects. Additionally,the radar processor may determine a location and a movement of thereflecting objects.

Additionally, in some examples, a first radar reflection of the tworadar reflections is received by a first radar unit of the radar systemand a second radar reflection of the two radar reflections is receivedby a second radar unit of the radar system. Thus, the two radar unitsmay each send and receive signals based on their respective fields ofview. However, a secondary reflecting object may cause a radar unit tohave a skewed field of view and the secondary reflecting object causesradar signals to reflect in a direction other than the transmitteddirection. In some other examples, one radar unit may receive both aprimary reflection signal and a secondary reflection signal.

For each of the two received radar reflections the system may determinea doppler, azimuth extent, and range for the reflections. Doppler is ameasure of the motion of the object in a direction normal to thedirection of the radar reflection. Azimuth extent is the angular widthof the object. Range is the distance to the reflecting object, measuredalong the path of the radar signal (including any secondaryreflections). As previously discussed, some radar systems may have arelatively high precision for range and doppler and a relatively lowprecision for azimuth. In practice, this means a radar system mayaccurately be able to measure the distance to and the normal-directedmotion of a reflecting object. However, the azimuth resolution may belower leading to a less accurate measure of the angular width of anobject. The present disclosure uses a multibounce radar signal toincrease the azimuth accuracy.

Additionally at block 704 (and/or at block 706), the system maydetermine a primary reflection of the two received radar reflections anda secondary reflection of the two received radar reflections. A primaryreflection is a reflection signal that only reflects once. For example,a radar unit may transmit a radar signal that reflects off anothervehicle before being received by the radar unit as a primary reflection.A secondary reflection is a reflection signal that has reflected morethan once before being received. For example, a radar unit may transmita radar signal that reflects off a secondary reflector before reflectingoff another vehicle before being received by the radar unit as a primaryreflection. In some examples, the secondary reflection may reflect offthe secondary reflector before reflecting off the target object, afterreflecting off the target object, or both before and after reflectingoff the target object.

At block 706, the method 700 includes determining, by the radarprocessing system, that two received radar reflections correspond to anobject in the environment, wherein at least one of the two receivedradar reflections had a reflection in the environment off a secondaryreflecting object. In some examples, block 706 may also perform thefunctions of block 606-610 of method 600 to receive the location ofknown objects in the environment of the vehicle, determine object'slocations, and determine secondary reflecting objects.

Based on the received radar signals, the radar processing system maytrack a plurality of objects that produce radar reflection. By trackingobjects, the radar system may determine a location and movement (e.g.,range, doppler, and azimuth extent) of the various objects that causedradar reflections. With each subsequent received radar pulse, the radarsystem may update the location information. Thus, through a series ofreceived radar pulses, the radar system may be able to revise thelocation information and track the relative locations of the variousreflectors.

In some examples, at block 706, a processor of the vehicle, such as theradar processor or another processor, may associate the trackedreflecting objects with various known objects. Thus, the tracking mayinclude a processor associating the radar reflection signals with knownobjects in the map data. The radar system may perform an analysis, suchas by raytracing or another algorithm, to determine two radarreflections that correspond to a single object. In some cases, one ofthe radar reflections may be a primary reflection and the other may be asecondary reflection. In another case, both radar reflections may besecondary reflections.

In some examples, block 706 may include determining a secondaryreflecting object that caused the incorrect location. At block 706, theprocessor may determine that a potential secondary reflecting object islocated in the environment of the vehicle. For example, this secondaryreflecting object may be an overhead road sign that is identified in themap data. In another example, the radar processing system may be able toidentify a secondary reflecting object based on received radarreflections (as the secondary reflecting object may also act as aprimary reflecting object and directly reflect radar signals back to thevehicle that transmitted the radar signals). Additionally, at block 706,the system may communicate information about the secondary reflectingobject to a remote computing system. For example, the vehicle may senddata to the remote computing system so that the remote computing systemmay update global map data (i.e., map data provided to all vehicles) sothat other vehicles may be able to more easily identify the secondaryreflecting object.

At block 708, the method 700 includes revising a tracking for theobject. In response to the system determining that two radar reflectionscorrespond to a single tracked object, the system may revise thetracking. In some examples, the system may revising the tracking byrevising a location of the object. In some additional examples, thesystem may revising the tracking by revising an azimuth extent for theobject based on at least one of the doppler, azimuth extent, and rangefor the secondary reflection.

As shown in FIG. 5, the two radar reflections (shown in FIG. 5 as aprimary reflection and a secondary reflection) are created by anotherobject. The extent of the azimuth ambiguity is in a different directionfor each of the two azimuth extents. Thus, using the range measurement(and possibly the doppler measurement) of the secondary reflection, thesystem may be able to accurately locate the vehicle along the path ofthe secondary radar reflection. Further, because there is a component ofthe secondary reflection that is orthogonal to the primary reflection,this range information may supplement the azimuth information of theprimary reflection. By supplementing the lower accuracy azimuthinformation for the primary reflection with higher accuracy rangeinformation from the secondary reflection, the system may be able torevise the azimuth information for the primary reflection. Thus, thesystem may revise the target information for the object that caused thetwo reflections based on the azimuth information that has been revisedbased on the information from the secondary reflection.

Although methods 600 and 700 are described as separate methods, in someexamples, various features of the two methods may be combined. Forexample, block 708 of method 700 may be performed at block 612 of method600. Other examples are possible as well. Moreover, both methods 600 and700 may contain another block that includes controlling a vehicle basedon the revised target information. Because both methods 600 and 700included revising information about radar signals, each method mayprovide more accurate information about the environment of the vehicle.Therefore, each method may also include controlling the vehicle, such asin an autonomous drive mode, based on either blocks 602-612 and/orblocks 702-708.

FIG. 8 depicts an example computer readable medium configured accordingto an example embodiment. In example embodiments, an example system mayinclude one or more processors, one or more forms of memory, one or moreinput devices/interfaces, one or more output devices/interfaces, andmachine readable instructions that when executed by the one or moreprocessors cause the system to carry out the various functions tasks,capabilities, etc., described above.

As noted above, in some embodiments, the disclosed techniques (e.g.,methods 400, etc.) may be implemented by computer program instructionsencoded on a computer readable storage media in a machine-readableformat, or on other media or articles of manufacture (e.g., instructions216 of the vehicle 200, instructions 312 of the computing device 304,etc.). FIG. 8 is a schematic illustrating a conceptual partial view ofan example computer program product that includes a computer program forexecuting a computer process on a computing device, such as on a radarplanning system, arranged according to at least some embodimentsdisclosed herein.

In one embodiment, the example computer program product 800 is providedusing a signal bearing medium 802. The signal bearing medium 802 mayinclude one or more programming instructions 804 that, when executed byone or more processors may provide functionality or portions of thefunctionality described above with respect to FIGS. 1-9. In someexamples, the signal bearing medium 802 may be a computer-readablemedium 806, such as, but not limited to, a hard disk drive, a CompactDisc (CD), a Digital Video Disk (DVD), a digital tape, memory, etc. Insome implementations, the signal bearing medium 802 may be a computerrecordable medium 808, such as, but not limited to, memory, read/write(R/W) CDs, R/W DVDs, etc. In some implementations, the signal bearingmedium 802 may be a communication medium 810 (e.g., a fiber optic cable,a waveguide, a wired communications link, etc.). Thus, for example, thesignal bearing medium 802 may be conveyed by a wireless form of thecommunications medium 810.

The one or more programming instructions 804 may be, for example,computer executable and/or logic implemented instructions. In someexamples, a computing device may be configured to provide variousoperations, functions, or actions in response to the programminginstructions 804 conveyed to the computing device by one or more of thecomputer readable medium 806, the computer recordable medium 808, and/orthe communications medium 810.

The computer readable medium 806 may also be distributed among multipledata storage elements, which could be remotely located from each other.The computing device that executes some or all of the storedinstructions could be an external computer, or a mobile computingplatform, such as a smartphone, tablet device, personal computer,wearable device, etc. Alternatively, the computing device that executessome or all of the stored instructions could be remotely locatedcomputer system, such as a server, or a distributed cloud computingnetwork.

It should be understood that arrangements described herein are forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g. machines,interfaces, functions, orders, and groupings of functions, etc.) can beused instead, and some elements may be omitted altogether according tothe desired results. Further, many of the elements that are describedare functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location, or other structural elementsdescribed as independent structures may be combined.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims, along with the full scope ofequivalents to which such claims are entitled. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

What is claimed is:
 1. A method comprising: transmitting a radar signalby a radar system; receiving reflections of the radar signal from anenvironment by the radar system; receiving a location of a plurality ofobjects in the environment by a radar processing system; tracking aplurality of reflecting objects in the environment based on the receivedreflections by the radar processing system; determining, by the radarprocessing system, that a received radar reflection corresponds to oneof the plurality objects in the environment having an incorrectlocation; and revising a tracking for the one of the plurality objectsin the environment having an incorrect location.
 2. The method of claim1, wherein revising the tracking comprises stopping tracking.
 3. Themethod of claim 1, wherein revising the tracking comprises revising alocation of the one of the plurality objects in the environment havingan incorrect location.
 4. The method of claim 3, wherein revising thetracking comprises revising a movement direction of the one of theplurality objects in the environment having an incorrect location. 5.The method of claim 1, wherein receiving a location of a plurality ofobjects in the environment comprises receiving object data from asensor.
 6. The method of claim 1, wherein receiving a location of aplurality of objects in the environment comprises receiving object datafrom map data stored in a memory.
 7. The method of claim 1, furthercomprising determining a secondary reflecting object that caused theincorrect location.
 8. The method of claim 1, further comprisingcommunicating the secondary reflecting object to a remote computingsystem.
 9. A radar system comprising: a radar unit configured to:transmit a radar signal, and receive radar reflections, a memoryconfigured to store data related to an environment; and a radarprocessing system configured to: receive a location of a plurality ofobjects in the environment, track a plurality of reflecting objects inthe environment based on the received radar reflections, determine thata received radar reflection corresponds to one of the plurality objectsin the environment having an incorrect location, and revise a trackingfor the one of the plurality objects in the environment having anincorrect location.
 10. The radar system of claim 9, further comprisinga communication system configured to receive object data from map datastored in a memory.
 11. The radar system of claim 9, further comprisinga communication system configured to receive object data from a sensor.12. The radar system of claim 9, wherein the radar processing system isfurther configured to revise the tracking by revising a location of theone of the plurality objects in the environment having an incorrectlocation.
 13. A non-transitory computer readable medium having storedthereon executable instructions that, upon execution by a computingdevice, cause the computing device to perform functions comprising:transmitting a radar signal by a radar system; receiving reflections ofthe radar signal from an environment by the radar system; receiving alocation of a plurality of objects in the environment by a radarprocessing system; tracking a plurality of reflecting objects in theenvironment based on the received reflections by the radar processingsystem; determining that a received radar reflection corresponds to oneof the plurality objects in the environment having an incorrect locationby the radar processing system; and revising a tracking for the one ofthe plurality objects in the environment having an incorrect location.14. The non-transitory computer readable medium of claim 13, whereinrevising the tracking further comprises instructions for stoppingtracking.
 15. The non-transitory computer readable medium of claim 13,wherein revising the tracking further comprises instructions forrevising a location of the one of the plurality objects in theenvironment having an incorrect location.
 16. The non-transitorycomputer readable medium of claim 15, wherein revising the trackingfurther comprises instructions for revising a movement direction of theone of the plurality objects in the environment having an incorrectlocation.
 17. The non-transitory computer readable medium of claim 13,wherein receiving a location of a plurality of objects in theenvironment further comprises instructions for receiving object datafrom a sensor.
 18. The non-transitory computer readable medium of claim13, wherein receiving a location of a plurality of objects in theenvironment further comprises instructions for receiving object datafrom map data stored in a memory.
 19. The non-transitory computerreadable medium of claim 13, further comprising instructions fordetermining a secondary reflecting object that caused the incorrectlocation.
 20. The non-transitory computer readable medium of claim 13,further comprising instructions for communicating the secondaryreflecting object to a remote computing system.